Projector

ABSTRACT

The invention achieves a reduction in size of a projector by shortening a length of an optical path of an illuminating optical system in a projector using an emitting direction control-type optical modulation device as compared to that of a conventional illuminating optical system, and thus, improves the illumination efficiencies of the illuminating optical system. An illuminating optical system includes a light source, a first lens array having a plurality of first small lenses for dividing light emitted from the light source into a plurality of partial light beam fluxes, and a second lens array having a plurality of second small lenses corresponding to the plurality of first small lenses. In addition, the illuminating optical system includes an optical element such that an outline shape of an emitting surface is a quadrilateral having first and second diagonal lines of different lengths. The quadrilateral of the optical element is set so that the ratio of two diagonal lines of a quadrilateral illumination region to which the illumination light is applied comes closer to I than the ratio of the lengths of the first and second diagonal lines.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The present invention relates to a projector for projecting anddisplaying an image.

[0003] 2. Description of Related Art

[0004] In a projector, image light representing an image is formed fromillumination light using an electrooptic device, and an image isdisplayed by projecting the image light. As the electrooptic device, anoptical modulation device (emitting direction control-type opticalmodulation device) for modulating the illumination light according tothe image information (image signal) and emitting the image lightrepresenting the image, is used. As an example of the optical modulationdevice, a micro-mirror-type optical modulation device, such as a DigitalMicro-mirror Device (registered trademark of Texas Instruments, Inc.;hereinafter, referred to as “DMD”) can be given.

[0005] The DMD has a plurality of micro-mirrors corresponding to aplurality of pixels constituting the image. The inclination of themicro-mirrors varies with image information, and the micro-mirrorsreflect light according to the inclination thereof. Of the lightreflected by the micro-mirrors, the light reflected in a predetermineddirection is used as the image light. That is, the DMD is anelectrooptic device of a type which controls the direction of reflectionof light so as to form image light.

[0006]FIG. 13 is a schematic plan view showing a construction of aprincipal part of a conventional projector using a micro-mirror-typeoptical modulation device. A projector 5000 includes an illuminatingoptical system 100E, a micro-mirror-type optical modulation device 200,and a projection lens 300.

[0007] The illuminating optical system 100E includes a light source 110,a first condenser lens 120, a color wheel 130, a light-transmitting rod180A, and a second condenser lens 190.

[0008] The light emitted from the light source 110 passes through thefirst condenser lens 120, the color wheel 130, the light-transmittingrod 180A, and the second condenser lens 190 to enter themicro-mirror-type optical modulation device 200. The light entered themicro-mirror-type optical modulation device 200 is modulated accordingto an image signal given to the micro-mirror-type optical modulationdevice 200. The light modulated by the micro-mirror-type opticalmodulation device 200 is projected as light representing an image (imagelight) via the projection lens 300, whereby an image is displayed.

[0009] There may be many cases where illuminance distribution of thelight emitted from the light source 110 is not uniform. When such lightis used as illumination light, there may be many cases where thebrightness of the displayed image is not uniform according to theilluminance distribution of the illumination light. However, an imagedisplayed by a projector may preferably have uniform brightness and bebright. Thus, in order to solve the problem, the light-transmitting rod180A has been often used as in the illuminating optical system 100E. Thelight-transmitting rod 180A is an optical element having the function ofemitting light whose illuminance distribution is uniform even if theilluminance distribution of incident light is not uniform.

[0010] The light-transmitting rod 180A is, however, an optical elementin which light entered from an incident-side side surface 180AI of thelight-transmitting rod 180A passes through the light-transmitting rod180A while being repeatedly reflected by the inner surface of thelight-transmitting rod 180A, thereby producing a uniform illuminancedistribution of light emitted from a side surface 180AO on the side ofan emitting surface. Therefore, in order to produce a uniformilluminance distribution of the light emitted from thelight-transmitting rod 180A, the light entered the light-transmittingrod 180A must be reflected many times by the inner surface of thelight-transmitting rod 180A. That is, the light-transmitting rod 180Arequires a length according to the illuminance distribution of the lightemitted from the light source 110, and the longer length is morepreferable. Consequently, in a projector which utilizes an illuminatingoptical system using a light-transmitting rod, the length of an opticalpath of the illuminating optical system (physical length of the opticalpath between a light source and a micro-mirror-type optical modulationdevice) is generally elongated, causing a problem in that a reduction insize of the device is difficult.

[0011] Incidentally, the brightness of the image displayed by theprojector greatly depends on the illuminance of an illumination regionto which the light emitted from the illuminating optical system isapplied. That is, in illuminating optical systems each emitting the sameamount of illumination light, the illuminance increases in theilluminating optical system having a small area of the illuminationregion to which the illumination light is applied, whereby the imagedisplayed by the projector is brightened. Therefore, the illuminatingoptical system of the projector may preferably have high illuminationefficiency to a light application surface of the electrooptic device.However, when an optical modulation device (emitting directioncontrol-type optical modulation device), such as the DMD, is used as anelectrooptic device for the projector, there is a problem in thatillumination efficiency of the illuminating optical system is decreasedby the positional relationship between the illuminating optical systemand the optical modulation device. In addition, this problem also occursin optical modulation devices for controlling the direction of emissionof illumination light applied to a light application surface (includinga plurality of pixels) according to image information (for each pixel)to thereby emit image light representing an image.

SUMMARY OF THE INVENTION

[0012] It is one aspect of this invention to provide a technique forachieving a reduction in size of a projector using an optical modulationdevice (emitting direction control-type optical modulation device) forcontrolling a direction of emission of illumination light applied to alight application surface for each pixel according to image informationto thereby emit image light representing an image, by shortening alength of an optical path (physical length of an optical path between alight source and the emitting direction control-type optical modulationdevice) of an illuminating optical system as compared to that of aconventional illuminating optical system. In addition, it is a secondobject of this invention to provide a technique for achieving anincrease in illumination efficiency of the illuminating optical system.

[0013] In order to solve at least a part of the above-describedproblems, in accordance with the first aspect of the present invention,there is provided a projector, that may include an illuminating opticalsystem for emitting illumination light, an optical modulation device formodulating the illumination light emitted from the illuminating opticalsystem, and a projection optical system for projecting light emittedfrom the optical modulation device, wherein the optical modulationdevice is an emitting direction control-type optical modulation devicefor controlling a direction of emission of illumination light applied toa light application surface of the optical modulation device accordingto a given image signal to modulate the illumination light, therebyemitting image light representing an image.

[0014] The illuminating optical system may include a light source, afirst lens array having a plurality of first small lenses for dividinglight emitted from the light source into a plurality of partial lightbeam fluxes, and a second lens array having a plurality of second smalllenses corresponding to the plurality of first small lenses.

[0015] The plurality of partial light beam fluxes divided by the firstlens array are applied onto the entire light application surface of theoptical modulation device via the second lens array, respectively. Thatis, the first lens array and the second lens array have the function ofuniformly illuminating the light application surface of the opticalmodulation device, similarly to a light-transmitting rod used in aconventional illuminating optical system.

[0016] A length of an optical path of the illuminating optical systemincluding the first lens array and the second lens array (physicallength between the light source and the optical modulation device) canbe easily adjusted according to setting of lens characteristics of thelens arrays. For this reason, the length of the optical path of theilluminating optical system can be easily shortened, as compared to theconventional illuminating optical system using the light-transmittingrod, whereby the size of a projector of the first aspect can be easilyreduced, as compared to a conventional projector.

[0017] In the above-described projector of the first aspect, at leastone of the plurality of first small lenses of the first lens array maybe a decentering lens. In addition, at least a part of the plurality ofsecond small lenses of the second lens array may be a decentering lens.If at least one of the plurality of first small lenses of the first lensarray and at least one of the plurality of second small lenses of thesecond lens array is a decentering lens that is set according to adirection of light incident thereon, the partial light beam flux emittedtherefrom can be efficiently applied to the light application surface ofthe optical modulation device.

[0018] In the above-described projector of the first aspect, theilluminating optical system may preferably include a first condenserlens, a color wheel having a plurality of color filters rotatably formedthereon, and a second condenser lens in order between the light sourceand the first lens array.

[0019] In addition, the illuminating optical system may include a firstcondenser lens, a color wheel having a plurality of color filtersrotatably formed thereon, and a second condenser lens in order betweenthe second lens array and the optical modulation device.

[0020] With these arrangements, it is possible to facilitate a reductionin the size of optical systems constituting a projector for displaying acolor image.

[0021] In accordance with a second aspect of the present invention,there is provided a projector that may include an optical modulationdevice for controlling a direction of emission of illumination lightapplied to a substantially rectangular light application surface,including a plurality of pixels, for each pixel according to imageinformation to thereby emit image light representing an image, anilluminating optical system for emitting the illumination light so thatthe central axis of the illumination light applied to the lightapplication surface enters the light application surface at apredetermined angle, and a projection optical system for projectingimage light emitted from the optical modulation device.

[0022] The illuminating optical system may include an optical elementsuch that an outline shape of an emitting surface is a quadrilateralhaving first and second diagonal lines of different lengths, and whenthe illumination light emitted from the optical element obliquely entersthe light application surface at the predetermined angle, thequadrilateral is set so that the ratio of two diagonal lines of aquadrilateral illumination region to which the illumination light isapplied is closer to 1 than the ratio of the lengths of the first andsecond diagonal lines.

[0023] According to the above-described projector of the second aspect,the outline shape of the illumination region can be brought closer tothe substantially rectangular light application surface even if theillumination light obliquely enters the light application surface at apredetermined angle. Therefore, the illumination efficiency of theillumination light applied to the light application surface of theoptical modulation device can be increased.

[0024] In the above-described projector of the second aspect, theilluminating optical system may preferably include a light source, afirst lens array having a plurality of first small lenses each beingequivalent to the optical element, and dividing the light emitted fromthe light source into a plurality of partial light beam fluxes, and asecond lens array having a plurality of second small lensescorresponding to the plurality of first small lenses.

[0025] With these arrangements, the illumination efficiency of each ofthe plurality of partial light beam fluxes applied to the lightapplication surface can be increased, and a uniform illuminancedistribution of the illumination light applied to the light applicationsurface can be produced.

[0026] Incidentally, each of the plurality of first lenses may be a lenshaving a parallelogram-shaped outline. With this arrangement, theplurality of first small lenses can be closely arranged without anyspaces, so that the light emitted from the light source entering thefirst lens array can be used more effectively by being divided into aplurality of partial light beam fluxes.

[0027] Here, at least one of the plurality of first small lenses of thefirst lens array may be a decentering lens. In addition, at least one ofthe plurality of second small lenses of the second lens array may be adecentering lens. If at least one of the plurality of first small lensesof the first lens array and at least a part of the plurality of secondsmall lenses of the second lens array is a decentering lens that is setaccording to a direction of light incident thereon, the partial lightbeam flux emitted therefrom can be efficiently applied to the lightapplication surface of the optical modulation device.

[0028] In the above-described projector of the second aspect, theilluminating optical system may preferably include a first condenserlens, a color wheel having a plurality of color filters rotatably formedthereon, and a second condenser lens in order between the light sourceand the first lens array.

[0029] In addition, the illuminating optical system may include a firstcondenser lens, a color wheel having a plurality of color filtersrotatably formed thereon, and a second condenser lens in order betweenthe second lens array and the optical modulation device.

[0030] With these arrangements, it is possible to facilitate a reductionin the size of optical systems constituting a projector for displaying acolor image.

[0031] Incidentally, in the above-described projector of the secondaspect, the illuminating optical system may preferably include a lightsource, and a light-transmitting rod equivalent to the optical element.

[0032] With these arrangements, the illumination efficiency of theillumination light applied to the light application surface can also beincreased, and a uniform illuminance distribution of the illuminationlight applied to the light application surface can be produced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a schematic plan view showing a construction of aprincipal part of a projector according to a first embodiment of thepresent invention;

[0034]FIG. 2 is a front view of a color wheel 130 as viewed from theside of a light source 110;

[0035] FIGS. 3(A)-3(C) include a front view showing a first lens array150D as viewed from the side of a light incident surface, a top view,and a side view thereof;

[0036]FIG. 4 is a front view showing a modification of a second lensarray 160D;

[0037]FIG. 5 is a schematic plan view showing a construction of aprincipal part of a projector according to a second embodiment of thepresent invention;

[0038] FIGS. 6(A)-6(C) include a front view showing a first lens array150 as viewed from the side of a light incident surface, a top view, anda side view thereof;

[0039] FIGS. 7(A)-7(C) include explanatory views each showing a DMD thatis an example of a micro-mirror-type optical modulation device 200;

[0040] FIGS. 8(A) and 8(B) include explanatory views each showingillumination light applied onto a light application surface 202;

[0041]FIG. 9 is a schematic plan view showing a construction of aprincipal part of a projector according to a third embodiment of thepresent invention;

[0042]FIG. 10 is a schematic plan view showing a construction of aprincipal part of a projector according to a fourth embodiment of thepresent invention;

[0043]FIG. 11 is a perspective view showing an external appearance of alight-transmitting rod 180;

[0044]FIG. 12 is a schematic plan view showing a construction of aprincipal part of a projector according to a fifth embodiment of thepresent invention; and

[0045]FIG. 13 is a schematic plan view showing a construction of aprincipal part of a conventional projector using a micro-mirror-typeoptical modulation device.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0046] Embodiments of the present invention will now be described withreference to the drawings. In the following embodiments, unlessotherwise specified, three mutually perpendicularly intersectingdirections are conveniently referred to as follows: the direction oftravel of light is referred to as the z-axis direction (directionparallel to an optical axis), the direction of 12 o'clock as viewed fromthe z-axis direction is referred to as the y-axis direction (verticaldirection), and the direction of 3 o'clock is referred to as the x-axisdirection (horizontal direction).

[0047]FIG. 1 is a schematic plan view showing a construction of aprincipal part of a projector according to a first embodiment of thepresent invention. A projector 1000A includes an illuminating opticalsystem 100D, a micro-mirror-type optical modulation device 200, and aprojection lens 300. The micro-mirror-type optical modulation device 200and the projection lens 300 are disposed so that central axes 200 ax and300 ax thereof coincide with each other.

[0048] The illuminating optical system 100D is disposed in such a mannerthat the central axis 100Dax of the illuminating optical system has apredetermined inclination relative to the central axis (normal line of alight application surface 202) 200 ax of the micro-mirror-type opticalmodulation device 200 due to the restriction of an incident angle oflight illuminating the micro-mirror-type optical modulation device 200.Here, the “light application surface” refers to a light applicationsurface in a narrow sense which is a region which the applied light canbe used as image light, that is, on which a micro-mirror describedhereinbelow is formed. In the following description, however, the entireregion to which light is applied including the outside of the region onwhich the micro-mirror is formed may be referred to as the lightapplication surface. Incidentally, as regards “predeterminedinclination”, a description will be omitted because it causes no problemin the first embodiment, but it will be described in detail in a secondembodiment.

[0049] The illuminating optical system 100D includes a light source 110,a first condenser lens 120, a color wheel 130, a second condenser lens140, a first lens array 150D, a second lens array 160D, and asuperimposing lens 170. These optical elements 110, 120, 130, 140, 150D,160D, and 170 are disposed in order along the central axis 100Dax of theilluminating optical system 100D.

[0050] The light source 110 has a light source lamp 112 and a concavemirror 114. The light source lamp 112 is a radiation light source foremitting radiating light beams. A high-pressure discharge lamp, such asa metal halide lamp or a high-pressure mercury lamp, is used as thelight source lamp 112. The concave mirror 114 is an ellipsoidal concavemirror for emitting radiating light beams from the light source lamp 112as condensed light from an opening 116 so that the radiating light beamsare reflected to enter the first condenser lens 120. As the concavemirror 114, a parabolic concave mirror for reflecting the radiatinglight beams from the light source lamp 112 and emitting them assubstantially parallel light, may be used. In this case, anothercondenser lens may be added between the light source 110 and thecondenser lens 120, so that the substantially parallel light enters thefirst condenser lens 120.

[0051] The first condenser lens 120 is an optical element for condensinglight from the light source 110 in the vicinity of the color wheel 130so as to reduce the size of a light spot applied to the color wheel 130.

[0052]FIG. 2 is a front view of the color wheel 130 as viewed from theside of the light source 110. The color wheel 130 has three transmissivecolor filters 130R, 130G, and 130B formed on three fan-shaped regionsthat are divided in a direction of rotation thereof. A first colorfilter 130R has the function of transmitting light in a red wavelengthregion (hereinafter, referred to as “red light R”) and of reflecting orabsorbing light in other wavelength regions. Similarly, second and thirdcolor filters 130G and 130B have the function of transmitting light in agreen wavelength region and light in a blue wavelength region(hereinafter, referred to as “green light G” and “blue light B”,respectively) and of reflecting or absorbing light in other wavelengthregions, respectively. The color filter is formed of, for example, adielectric multilayer film or a filter sheet formed by using a dye.

[0053] The color wheel 130 is disposed so that a light spot SP condensedby the first condenser lens 120 is applied to a predetermined peripheralposition deviating from a central axis 130 ax of the color wheel 130.The color wheel 130 is rotated by a motor (not shown) about the rotationaxis 130 ax at a constant speed. In this case, the light spot SPcyclically illuminates the regions of the color filters 130R, 130G, and130B at constant intervals in accordance with the rotation of the colorwheel 130. Consequently, the light transmitted by the color wheel 130 iscyclically changed to the red light R, the green light G, and the bluelight B in accordance with the rotation of the color wheel 130.

[0054] The second condenser lens 140 shown in FIG. 1 has the function ofcondensing light transmitted by the color wheel 130 so that the lightenters the first lens array 150D. In this embodiment, the secondcondenser lens 140 is set so that divergent light transmitted by thecolor wheel 130 becomes substantially parallel light.

[0055] The first lens array 150D is a lens array composed of a pluralityof first small lenses 152D. The first lens array 150D has the functionof dividing the substantially parallel light emitted from the secondcondenser lens 140 into a plurality of partial light beam fluxescorresponding to the plurality of first small lenses 152, and ofcondensing the partial light beam fluxes in the vicinity of the secondlens array 160D.

[0056] FIGS. 3(A)-3(C) include a front view showing the first lens array150D as viewed from the side of the light incident surface, a top view,and a side view thereof. As shown in FIG. 3(A), the first lens array150D has a construction such that the first small lenses 152D, which aresubstantially rectangular concentric lenses, are arranged in the form ofa matrix with M rows and N columns. FIGS. 3(A)-3(C) show an example inwhich M=4, and N=3. The “concentric lens” refers to a lens in which ageometric center and an optical center of the lens coincide with eachother.

[0057] The second lens array 160D includes second small lenses 162Dcorresponding to the first small lenses 152D of the first lens array150D. The second lens array 160D has the function of forming an image ofthe first lens array 150D on an application surface of themicro-mirror-type optical modulation device 200 via the superimposinglens 170. The second small lenses 162D of the second lens array 160D mayhave any shape as long as the corresponding partial light beam fluxesemitted from the first lens array 150D can enter. In this embodiment, alens array, which is different from the first lens array 150D only in adirection of lens surface (convex surface), is used.

[0058] The superimposing lens 170 has the function of superimposing aplurality of partial light beam fluxes emitted from the second lensarray 160 on an application surface of the micro-mirror-type opticalmodulation device 200.

[0059] A plurality of partial light beam fluxes emitted from the firstlens array 150D pass through the second lens array 160D and thesuperimposing lens 170 to illuminate a light application surface 202 ofthe micro-mirror-type optical modulation device 200, whereby the lightapplication surface 202 is uniformly illuminated even if light emittedfrom the light source 110 has illuminance distribution.

[0060] The micro-mirror-type optical modulation device 200 is an opticalmodulation device for emitting image light representing an image towardthe projection lens 300 by reflecting the illumination light applied tothe light application surface by micro-mirrors corresponding to pixelsaccording to an image signal (image information). The image lightemitted from the micro-mirror-type optical modulation device 200 isprojected via the projection lens 300, whereby an image is displayed.

[0061] As described above, the illuminating optical system 100D of theprojector 1000A in this embodiment realizes the function similar to thatof the light-transmitting rod 180A of the conventional illuminatingoptical system 100E (FIG. 13) by an integrator optical system composedof the first lens array 150D, the second lens array 160D, and thesuperimposing lens 170.

[0062] The physical length between the first lens array 150D and themicro-mirror-type optical modulation device 200 can be determined by therelationship of focal lengths among the optical elements of the firstlens array 150D, the second lens array 160D, and the superimposing lens170, and does not depend on the illuminance distribution of the lightemitted from the light source 110. In addition, the focal length of eachof the optical elements can be freely set in some degree. Therefore, ascompared to a case where the illuminating optical system having thelength of the optical path depending on the illuminance distribution isused, as described in a conventional example, the length of the opticalpath of the illuminating optical system can be shortened, whereby areduction in size of the projector can be achieved, as compared to theconventional projector.

[0063] In this embodiment, although a plurality of first small lenses152D of the first lens array 150D are substantially rectangular lenses,they are not limited thereto, and they may be lenses each having apentagonal or a hexagonal outline shape. That is, they may be formed inany shape as long as they can divide the light emitted from the lightsource 110 into a plurality of partial light beam fluxes.

[0064] In addition, although the second small lenses 162D of the secondlens array 160D are composed of concentric lenses similarly to the firstsmall lenses 152D of the first lens array 150D, they are not limitedthereto. For example, a modification shown below can be made.

[0065]FIG. 4 is a front view showing a modification of the second lensarray 160D.

[0066] In a second lens array 160D′ shown in FIG. 4, each of the secondsmall lenses 162D′ is composed of a decentering lens. The “decenteringlens” refers to a lens in which an optical center (shown by +) of thelens are shifted from a position of a geometric center (shown by ).

[0067] A plurality of partial light beam fluxes divided by the firstlens array 150D may not efficiently be superimposed on the lightapplication surface 202 of the micro-mirror-type optical modulationdevice 200 due to spherical aberration of the superimposing lens 170shown in FIG. 1, whereby illumination efficiency may be decreased. Insuch a case, the influence of spherical aberration of the superimposinglens 170 can be suppressed by using the second lens array 160D′ shown inFIG. 4, so that the plurality of partial light beam fluxes can besufficiently superimposed on the light application surface 202 of themicro-mirror-type optical modulation device 200, and a decrease inillumination efficiency can be suppressed.

[0068] In addition, the illumination efficiency of the micro-mirror-typeoptical modulation device 200 to the light application surface 202 maybe decreased when parallelism of the light entering the first lens array150D is bad. In such a case, a decrease in illumination efficiency canbe suppressed by the first small lenses 152D of the first lens array150D by being composed of decentering lenses.

[0069] Furthermore, the first lens array 150D and the second lens array160D may be composed of decentering lenses.

[0070] Although the central axis 300 ax of the projection lens 300 isdisposed so as to coincide with the central axis 200 ax of themicro-mirror-type optical modulation device 200 in the projector 1000Aof the above-described embodiment, the disposition of the central axis300 ax is not limited thereto. The central axis 300 ax of the projectionlens 300 may be disposed by being shifted from the central axis 200 axof the micro-mirror-type optical modulation device 200. This can realizeshifting projection.

[0071] In the projector 1000A of the above-described embodiment,although an example of the color wheel 130 has been shown in which thethree transmissive color filters 130R, 130G, and 130B are formed on theregion divided into three equal parts along the direction of rotationthereof, the color wheel is not limited thereto. For example, the regionmay not be divided into three equal parts, but the area of the region tobe divided may be varied in accordance with the color valance. Inaddition, the region may be divided into six equal parts of red, green,blue, red, green, and blue. Alternatively, the region may be dividedinto four equal parts, and one of them may be colorless and transparent.In this case, if the rotation of the color wheel is stopped so that thelight from the light source 110 passes through only the colorless andtransparent region, a monochrome image can be displayed. In addition,instead of color filters of red, green, and blue, color filters capableof displaying a color image, for example, color filters of cyan,magenta, and yellow may be used. In the present invention, “colorfilters” include not only those having the function of transmittinglight in a specific wavelength region and of reflecting or absorbinglight in other wavelength regions, but also those having the function oftransmitting light in each of wavelength regions (function of atransparent region).

[0072] In addition, although the projector 1000A of the above-describedembodiment is a device including the color wheel 130 and displaying acolor image, the color wheel 130 may be omitted so as to display amonochrome image. In this case, the first condenser lens 120 and thesecond condenser lens 140 may also be omitted. In addition, the concavemirror 114 of the light source 110 may be a parabolic concave mirror soas to allow substantially parallel light to enter the first lens array150D.

[0073] The directions of the lens surfaces (convex surfaces and concavesurfaces) of the optical elements 120, 140, 150D, 160D, and 170 are notlimited to the directions shown in FIG. 1. They can also face in thereverse direction, and the directions of the lens surfaces of theoptical elements may be arbitrary combined. In addition, each of theoptical elements 120, 140, 150D, 160D, 170, and 300 may be formed by acompound lens having a plurality of combined lenses. Also, opticalelements adjacent to each other can be bonded and combined. For example,the second condenser lens 140 and the first lens array 150D can bebonded and combined. In addition, the second lens array 160D and thesuperimposing lens 170 can be bonded and combined. Furthermore, it ispossible to replace a plurality of optical elements with a singleoptical element. For example, the function of the superimposing lens 170can be imparted to the second lens array 160D to thereby omit thesuperimposing lens 170. It is also possible to omit any one of theoptical elements. For example, the first condenser lens 120 or thesecond condenser lens 140 can be omitted.

[0074] In addition, a prism utilizing the internal reflection may beprovided between the micro-mirror-type optical modulation device 200 andthe projection lens 300 to allow the illumination light emitted from theilluminating optical system 100C so as to be totally reflected by thelight application surface 202 of the micro-mirror-type opticalmodulation device 200, and the image light emitted from themicro-mirror-type optical modulation device 200 may be transmitted so asto be emitted toward the projection lens 300.

[0075] Incidentally, the above-described modifications can also beapplied to the following embodiments.

[0076]FIG. 5 is a schematic plan view showing a structure of a principalpart of a projector according to a second embodiment of the presentinvention. A projector 1000 includes an illuminating optical system 100,a micro-mirror-type optical modulation device 200, and a projection lens300. The difference between the projector 1000 and the projector 1000Aof the first embodiment is that the illuminating optical system 100D isreplaced by the illuminating optical system 100, and other respects aresimilar to those of the first embodiment. Constructions similar to thoseof the first embodiment are indicated by the same reference numerals,and a detailed description thereof will be omitted.

[0077] The illuminating optical system 100 is, as described also in thefirst embodiment, disposed in such a manner that the central axis 100 axof the illuminating optical system has a predetermined inclinationrelative to the central axis (normal line of a light application surface202) 200 ax of the micro-mirror-type optical modulation device 200 dueto the restriction of an incident angle of light illuminating themicro-mirror-type optical modulation device 200.

[0078] A first lens array 150 is a lens array composed of a plurality ofsmall lenses 152. Similarly to the first lens array 150D (FIG. 1), thefirst lens array 150 has the function of dividing substantially parallellight emitted from second condenser lens 140 into a plurality of partiallight beam fluxes corresponding to the first small lenses 152, and ofcondensing the partial light beam fluxes in the vicinity of a secondlens array 160.

[0079] FIGS. 6(A)-6(C) include a front view showing the first lens array150 as viewed from the side of the light incident surface, a top view,and a side view thereof. As shown in FIG. 6(A), the first lens array 150has a construction such that the first small lenses 152 are arranged inthe form of a matrix with M rows and N columns. FIGS. 6(A)-6(C) show anexample in which M=4, and N=3. The outline of each of the small lenses152 is a parallelogram such that a length of a diagonal line 152CR1obtained by connecting lower left and upper right vertexes is longerthan a length of a diagonal line 152CR2 obtained by connecting upperleft and lower right vertexes. The small lenses 152 are closely disposedwith sides thereof being in contact with each other. Therefore, theoutline of the first lens array 150 as the entire lens is also aparallelogram formed by sides parallel to the sides of the small lens152. The shape of the first lens array 150 will be farther describedhereinbelow.

[0080] The second lens array 160 includes small lenses 162 correspondingto the small lenses 152 of the first lens array 150. Similarly to thesecond lens array 160D (FIG. 1), the second lens array 160 has thefunction of forming an image of the first lens array 150 on anapplication surface of the micro-mirror-type optical modulation device200 via the superimposing lens 170. Incidentally, each of the smalllenses 162 of the second lens array 160 may have any shape other thanthe parallelogram as long as the corresponding partial light beam fluxesemitted from the first lens array 150 can enter. In this embodiment, alens array, which is different from the first lens array 150 only in adirection of lens surface (convex surface), is used.

[0081] The micro-mirror-type optical modulation device 200 is an opticalmodulation device for emitting image light representing an image towardthe projection lens 300 by reflecting the illumination light applied tothe light application surface by a micro-mirror corresponding to each ofpixels according to image information (image signal). FIGS. 7(A)-7(C)includes explanatory views each showing a DMD that is an example of themicro-mirror-type optical modulation device 200. As shown in FIG. 7(A),a plurality of micro-mirrors 204, each having a substantially squareoutline, are formed on the light application surface 202 of the DMD 200in the form of a matrix. Each of the micro-mirrors 204 is formed to berotatable about a rotation axis 204 c, which is a diagonal line obtainedby connecting lower left and upper right vertexes thereof, within apredetermined angular range. These micro-mirrors 204 correspond topixels constituting the image.

[0082] Here, to simplify the description, the illumination light appliedto the light application surface 202 is indicated by a central ray(incident ray) IR representing the illumination light. In addition, ahorizontal axis passing through an incident position of the illuminationlight IR to the light application surface 202 and is parallel to thex-axis is referred to as h, and the vertical axis parallel to the y-axisis referred to as v. In order to simplify the construction of thedevice, the illumination light IR applied to the DMD 200 may preferablyhave an incident surface perpendicular to the rotation axes 204 c of themicro-mirrors 204. For this reason, the illumination light IR applied tothe DMD 200, as shown in FIG. 7(A), is allowed to enter in a directiondiagonally from the lower right so that an inclination Oh of the opticalpath of the illumination light IR projected on the x-y plane parallel tothe light application surface 202 relative to the horizontal axis h isabout 45 degrees. In addition, as shown in FIG. 7(B), the illuminationlight IR is allowed to enter so that an incident angle θL to the lightapplication surface 202 is about 20 degrees in a plane that isperpendicular to the light application surface 202 and including theoptical path of the illumination light IR.

[0083]FIG. 7(C) shows an incident surface including the light incidenton the micro-mirror 204 and the light reflected therefrom, that is, anoptical path in a cross section perpendicular to the rotation axis 204c. The micro-mirror 204 is rotated about ±(θL/2) degrees (à±10 degrees)about the rotation axis 204 c relative to a plane F (shown by a brokenline in FIG. 7(C)) parallel to the light application surface 202. Anglesalong a clockwise direction are referred to as positive angles. Asdescribed above, the illumination light IR enters the micro-mirror 204from a direction inclined ±θL (à±20 degrees) relative to the normal lineFn of the plane F.

[0084] When the micro-mirror 204 is inclined by +(θL/2) relative to theplane F, the illumination light IR is emitted as reflected light RR(+θL/2) in a direction inclined by −θL relative to the illuminationlight IR, that is, in a direction parallel to the normal line Fn. Whenthe micro-mirror 204 is inclined by −(θL/2), the illumination light IRis emitted as reflected light RR (−θL/2) in a direction inclined by−(3·θL). In this way, the illumination light IR applied to themicro-mirror 204 is reflected and emitted in different directionsaccording to the rotation angle of the micro-mirror 204. For example,when the projection lens is disposed in the direction of the reflectedlight RR (+θL/2), only the reflected light RR (+θL/2) is used as imagelight. In this way, in a state where the micro-mirror 204 is inclined by+(L/2), the reflected light is projected via the projection lens torealize a bright display, and in a state where the micro-mirror lens 204is inclined by −(θL/2), the reflected light is not projected via theprojection lens to realize a dark display. An intermediate gradation isrealized by a method for controlling the ratio of bright and darkdisplays according to the gradation in a fixed time in which one pixeldraws an image (a so-called pulse width modulation method).

[0085] In the projector 1000 of this embodiment, the projection lens 300is disposed in such a manner that the reflected light in a state wherethe micro-mirror 204 is inclined by +(θL/2) is used as the image light.This allows the image light emitted from the micro-mirror-type opticalmodulation device 200 according to image information to be projected viathe projection lens 300, and an image is thereby displayed.

[0086] In addition, the red light R, the green light G, and the bluelight B are cyclically emitted at constant intervals from theilluminating optical system 100 according to the rotation of the colorwheel 130. In this case, by controlling the micro-mirrors 204 of themicro-mirror-type optical modulation device 200 according to the imageinformation corresponding to the applied color light, a color image canbe displayed.

[0087] The projector 1000 of the present invention is, as describedabove, characterized by the shape of the first lens array 150. That is,as shown in FIGS. 6(A)6(C), the device is characterized in that theoutline of the first lens array 150 and a plurality of small lenses 152constituting the first lens array 150 is a parallelogram. The first lensarray 150 is formed in the above shape for the following reasons.

[0088] As described above, the illumination light of the illuminatingoptical system 100 is applied to the micro-mirror-type opticalmodulation device 200 not from the direction of the normal line of thelight application surface 202 but from the direction having a fixedinclination relative to the normal line (FIGS. 7(A)-7(C)). FIGS. 8(A)and 8(B) include explanatory views each showing the illumination lightapplied onto the light application surface 202. If the small lenses 152of the first lens array 150 are composed of substantially rectangularlenses, the illumination region Fl of the illumination light applied soas to include the light application surface 202 is not of asubstantially rectangular shape, but of an irregular shape according tothe incident angle thereof.

[0089] As described with reference to FIGS. 7(A)-7(C), the illuminationregion FI when the illumination light is applied in a directiondiagonally from the lower right is of a quadrilateral such that thelength of a diagonal line FI2 obtained by connecting upper left andlower right vertexes is longer than the length of a diagonal line FI1obtained by connecting upper right and lower left vertexes, as shown inFIG. 8(A). When the illumination region FI is not of a substantiallyrectangular shape but is irregular, the ratio of ineffective light thatis not applied to the light application surface 202 is increased. Forthis reason, the illumination efficiency of the illumination lightemitted from the illuminating optical system 100 is decreased. In orderto decrease such ineffective light, the shape of the illumination lightemitted from the illuminating optical system 100 may be distorted inadvance so that the illumination region FI has a substantiallyrectangular shape.

[0090] That is, as shown in FIG. 8(B), of two diagonal lines RI1 and RI2of a cross section RI perpendicular to the central axis of theillumination light emitted from the illuminating optical system 100, thelonger diagonal line RI1 may be set so as to correspond to a longerdiagonal line FI2 of the distorted illumination region FI, and theshorter diagonal line RI2 may be set so as to correspond to a shorterdiagonal line FI1 of the distorted illumination region FI. In otherwords, the illuminating optical system may include an optical element inwhich an outline shape of an emitting surface is a quadrilateral havingfirst and second diagonal lines of different lengths, and when theillumination light emitted from the optical element obliquely enters alight application surface at a predetermined angle, the quadrilateralmay be set so that the ratio of two diagonal lines of a quadrilateralillumination region to which the illumination light is applied comescloser to 1 than the ratio of the lengths of the first and seconddiagonal lines. This can increase the illumination efficiency of theilluminating optical system.

[0091] In the projector 1000 of the present invention, each of the smalllenses 152 constituting the first lens array 150 of the illuminatingoptical system 100 has an outline shape of a parallelogram, as shown inFIGS. 6(A)-6(C). The outline of the parallelogram has, similarly to thecross section RI of the illumination light, a shape such that the lengthof a lens diagonal line 152CR1 of the small lens 152 corresponding to across sectional diagonal line RI1 is shorter than a lens diagonal line152CR2 corresponding to a cross sectional diagonal line RI2. This candecrease ineffective light that is not applied to the light applicationsurface 202. This can increase the illumination efficiency of thepartial light beam fluxes emitted from the small lenses 152. Inaddition, since the small lens 152 has an outline shape of aparallelogram, the small lenses 152 can be closely arranged. This allowsthe light emitted from the light source 110 to be effectively used, thusproviding excellent utilizing efficiency of the light emitted from thelight source 110. In this case, in order to allow the illumination lightemitted from the illuminating optical system 100 to be used moreeffectively. The lens arrays 150 and 160 may be actually preferablyrotated about the central optical axes thereof to adjust the shape ofthe illumination region.

[0092] In addition, in order to further increase light utilizingefficiency of the partial light beam fluxes emitted from the first lensarray 150, the shape of each of the small lenses 152 of the first lensarray 150 as viewed from the side of a light incident surface maypreferably be similar to the shape of the cross section RI shown in FIG.8(B). This allows the illumination region of the partial light beamfluxes emitted from the small lenses 152 to be brought closer to theoutline of the substantially rectangular light application surface 202,so that the illumination efficiency of the partial light beam fluxes canbe further increased. In this case, however, the small lenses 152 maynot be closely arranged, so that the utilizing efficiency of the lightemitted from the light source 110 may be decreased.

[0093] As described above, since the projector 1000 of the presentinvention can decrease ineffective light in the illumination lightilluminating the light application surface 202 of the micro-mirror-typeoptical modulation device 200, the illumination efficiency of theillumination light emitted from the illuminating optical system 100 canbe increased. In addition, similarly to the first embodiment, theilluminating optical system 100 includes an integrator optical systemcomposed of the first lens array 150, the second lens array 160, and thesuperimposing lens 170. Therefore, since the light application surface202 of the micro-mirror-type optical modulation device 200 is uniformlyilluminated by the illuminating optical system 100, an image havinguniform brightness can be displayed. In addition, the length of theoptical path of the illuminating optical system can be shortened ascompared to that of the conventional illuminating optical system. Thiscan achieve a reduction in size of the projector as compared to theconventional projector.

[0094] In this embodiment, although the DMD shown in FIGS. 3(A)-3(C),has been described as an example of the micro-mirror-type opticalmodulation device 200, the micro-mirror-type optical modulation device200 is not limited thereto. For example, various modes of the incidentangle of the illumination light may be considered according to thedirection of the rotation axes and the rotation range of themicro-mirrors 204. According to this, various modes of the shape of thesmall lens 152 of the first lens array 150 may be considered. Forexample, when the inclination θL of the illumination light relative tothe normal line of the light application surface 202 is larger than thevalue shown in FIGS. 6(A)-6(C), the small lens 152 can be formed in ashape of a parallelogram having a larger ratio of two lens diagonallines. In addition, in this embodiment, although a case has beendescribed where the DMD is applied as the micro-mirror-type opticalmodulation device, the micro-mirror-type optical modulation device isnot limited thereto, and various emitting direction control-type opticalmodulation devices for reflecting illumination light applied to thelight application surface according to image information to thereby emitimage light representing an image, can be used.

[0095] In addition, a prism utilizing the internal reflection may beprovided between the micro-mirror-type optical modulation device 200 andthe projection lens 300 to allow the illumination light emitted from theilluminating optical system 100 to be totally reflected by the lightapplication surface 202 of the micro-mirror-type optical modulationdevice 200, and the image light emitted from the micro-mirror-typeoptical modulation device 200 may be transmitted to be emitted towardthe projection lens 300.

[0096] Incidentally, the above-described modifications can also beapplied to the following embodiments.

[0097]FIG. 9 is a schematic plan view showing a structure of a principalpart of a projector according to a third embodiment of the presentinvention. A projector 2000 includes an illuminating optical system100A, a micro-mirror-type optical modulation device 200, and aprojection lens 300. The difference between the projector 2000 and theprojector 1000 (FIG. 5) of the second embodiment is that theilluminating optical system 100 is replaced by the illuminating opticalsystem 100A, and other respects are similar to those of the secondembodiment. Constructions similar to those of the second embodiment areindicated by the same reference numerals, and a detailed descriptionthereof will be omitted.

[0098] The difference between the illuminating optical system 100A ofthis embodiment and the illuminating optical system 100 of the secondembodiment is that a first lens array 150A and a second lens array 160Aare provided between a light source 110 and a first condenser lens 120A.The first lens array 150A has, similarly to the first lens array 150(FIGS. 6(A)-6(C)) small lenses 152A each having an outline shape of aparallelogram. The first lens array 150A divides condensed light emittedfrom the light source 110 into a plurality of partial light beam fluxes.The small lenses 162A constituting the second lens array 160A, may havesuch a construction as to include the partial light beam fluxes emittedfrom the first lens array 150A, as described above. Therefore, the shapeof the second lens array 160A may be smaller than the first lens array150A. The functions of the optical elements are the same except thefirst condenser lens 120A.

[0099] The light emitted from the light source 110 is divided into aplurality of partial light beam fluxes by the first lens array 150A toenter the first condenser lens 120A via the second lens array 160A. Thefirst condenser lens 120A has the function of superposing the enteredpartial light beam fluxes on a color wheel 130 to form an optical spotSP. The partial light beam fluxes emitted from the color wheel 130 entera superimposing lens 170 via a second condenser lens 140, and aresuperimposed on a light application surface 202 of the micro-mirror-typeoptical modulation device 200.

[0100] Since the projector 2000 of the third embodiment can alsodecrease ineffective light in the illumination light illuminating thelight application surface 202 of the micro-mirror-type opticalmodulation device 200, the illumination efficiency of the illuminationlight emitted from the illuminating optical system 100A can beincreased. In addition, similarly to the first embodiment, theilluminating optical system 100A includes an integrator optical systemcomposed of the first lens array 150A, the second lens array 160A, andthe superimposing lens 170. Therefore, since the light applicationsurface 202 of the micro-mirror-type optical modulation device 200 isuniformly illuminated by the illuminating optical system 100A, an imagehaving uniform brightness can be displayed. In addition, the length ofthe optical path of the illuminating optical system can be shortened ascompared to that of the conventional illuminating optical system. Thiscan achieve a reduction in size of the projector as compared to theconventional projector.

[0101]FIG. 10 is a schematic plan view showing a structure of aprincipal part of a projector according to a fourth embodiment of thepresent invention. A projector 3000 includes an illuminating opticalsystem 100B, a micro-mirror-type optical modulation device 200, and aprojection lens 300. The difference between the projector 3000 and theprojector 1000 (FIG. 5) of the second embodiment is that theilluminating optical system 100 is replaced by the illuminating opticalsystem 100B, and other respects are similar to those of the secondembodiment. Constructions similar to those of the second embodiment areindicated by the same reference numerals, and a detailed descriptionthereof will be omitted.

[0102] The illuminating optical system 100B includes a light source 110,a first condenser lens 120, a color wheel 130, a light-transmitting rod180, and a second condenser lens 190. The difference between theilluminating optical system 100B and the illuminating optical system 100of the second embodiment is that the illuminating optical system 100Bincludes the light-transmitting rod 180 and the second condenser lens190 instead of the lens arrays 150 and 160, and the superimposing lens170.

[0103] The illumination light passes through the light-transmitting rod180 while being repeatedly reflected by the inner surface of thelight-transmitting rod 180. Consequently, the light-transmitting rod 180has the function of emitting light of a uniform illuminance distributionfrom an emitting-side side surface 180O even if the illuminancedistribution of light emitted from the light source 110 is not uniform.That is, the light-transmitting rod 180 has the function of anintegrator optical system, similarly to the first and second lens arrays150 and 160, and the superimposing lens 170 of the illuminating opticalsystem 100. The second condenser lens 190 has the function of forming animage of an emitting surface of the light-transmitting rod 180 on thelight illumination surface 202 of the micro-mirror-type opticalmodulation device 200.

[0104]FIG. 11 is a perspective view showing an external appearance ofthe light-transmitting rod 180. The light-transmitting rod 180 is aquadrangular prism having an outline of a parallelogram as viewed fromthe side of the light source 110, similarly to the small lens 152 (FIGS.6(A)-6(C)) of the first lens array 150. This allows the projector 3000of the fourth embodiment to decrease ineffective light in theillumination light illuminating the light application surface 202 of themicro-mirror-type optical modulation device 200. Consequently, theillumination efficiency of the illumination light emitted from theilluminating optical system 100B can be increased. In addition, sincethe light application surface 202 of the micro-mirror-type opticalmodulation device 200 is uniformly illuminated by the illuminatingoptical system 100B, an image having uniform brightness can bedisplayed. In this case, in order to allow the illumination lightemitted from the illuminating optical system 100B to be used moreeffectively, the light-transmitting rod 180 may be actually preferablyrotated about the central optical axis thereof to adjust the shape ofthe illumination region.

[0105] In addition, the shape of the light-transmitting rod 180 asviewed from the side of the light source 110 may be similar to the shapeof the cross section RI shown in FIG. 8(B). This allows the illuminationregion FI of the light emitted from the light-transmitting rod 180 to besimilar to the outline of the light application surface 202.Consequently, the illumination efficiency owing to the light emittedfrom the light-transmitting rod 180 can be increased. Incidentally, atleast only the outline of the emitting surface of the light-transmittingrod 180 may be similar to the cross section RI shown in FIG. 8(B). Thatis, when the light emitted from the light-transmitting rod obliquelyenters the light application surface at a predetermined angle, thelight-transmitting rod may be set so that the ratio of the lengths oftwo diagonal lines of the quadrilateral illumination region to which theillumination light is applied comes closer to 1 than at least the ratioof the two diagonal lines of the emitting surface of thelight-transmitting rod. This can increase the illumination efficiencyowing to the light emitted from the light-transmitting rod.

[0106]FIG. 12 is a schematic plan view showing a construction of aprincipal part of a projector according to a fifth embodiment of thepresent invention. A projector 4000 includes an illuminating opticalsystem 100C, a color light separating-synthesizing prism 400, threemicro-mirror-type optical modulation devices 200R, 200G, and 200B, and aprojection lens 300. The projector 4000 is characterized by includingthe three micro-mirror-type optical modulation devices 200R, 200G, and200B and the color light separating-synthesizing prism 400.

[0107] The illuminating optical system 100C includes a light source110A, a first lens array 150, a second lens array 160, and asuperimposing lens 170. The difference between the illuminating opticalsystem 100C and the illuminating optical system 100 shown in FIG. 5, isthat the light source 110 is replaced by the light source 110A foremitting substantially parallel light, and that the first condenser lens120, the color wheel 130, and the second condenser lens 140 are omitted.Therefore, unlike the illuminating optical system 100 emittingcyclically the red light R, the green light G, and the blue light B, theilluminating optical system 100C emits illumination light includingrespective color light.

[0108] The light source 110A includes a light source lamp 112, and aconcave mirror (parabolic concave mirror) 114A in which the concavesurface is a parabolic surface, and emits substantially parallel lightfrom an opening 116.

[0109] The color light separating-synthesizing prism 400 has a structuresuch that three prisms 420, 430, and 440 are bonded one to the other. Ablue light-reflecting film BFIL is formed between a side surface 420R ofa first prism 420 and a side surface 430I of a second prism 430 whichare bonded to each other. In addition, a red light-reflecting film RFILis formed between a side surface 430R of the second prism 430 and a sidesurface 440I of a third prism 440 which are bonded to each other. Thesereflecting films BFIL and RFIL are usually formed of a dielectricmultilayer film.

[0110] On one side surface 430O of side surfaces of the second prism 430excluding the side surfaces 4301 and 430R, there is provided amicro-mirror-type optical modulation device 200R for the red light R. Ona side surface 420O opposing the micro-mirror-type optical modulationdevice 200R of side surfaces of the first prism 420 into which lightfrom the illuminating optical system 100C enters and the side surface420R bonded to the second prism 430, there is provided amicro-mirror-type optical modulation device 200B for the blue light B.On a side surface 440O of the third prism 440 perpendicular to thecentral axis 300 ax of the projection lens 300, there is provided amicro-mirror-type optical modulation device 200G for the green light G.These micro-mirror-type optical modulation devices 200R, 200G, and 200Bare not necessarily provided in contact with the side surfaces 420O,430O, and 440O.

[0111] The light emitted from the illuminating optical system 100C andincluding the red light R, the green light G, and the blue light Benters from the side surface 420I of the first prism 420 to enter theblue light-reflecting film BFIL. In order to simplify the description,light passing through the color light separating-synthesizing prism 400and thereafter, only the central light beam (one-dot chain line) isrepresentatively shown in the drawing.

[0112] Of the light entered the blue light-reflecting film BFIL, theblue light B is reflected by the blue light-reflecting film BFIL. Theblue light B reflected by the BFIL is usually divided into lighttransmitted by the side surface 420I and light reflected by the sidesurface 420I. The blue light B reflected by the side surface 420I entersthe micro-mirror-type optical modulation device 200B for the blue lightB. Incidentally, if the incident angle of the light reflected by theblue light-reflecting film BFIL on the side surface 420I is large, theratio of the reflected light can be increased. Furthermore, if theincident angle is increased to a critical angle or larger, the light canbe totally reflected. Such adjustment of the incident angle can berealized by adjusting angles made by the side surfaces of the prism 420with one to the other.

[0113] The micro-mirror-type optical modulation device 200B forms andemits blue image light FB from the entered blue light B. The blue imagelight FB emitted from the micro-mirror-type optical modulation device200B is reflected by the side surface 420I, and is further reflected bythe blue light-reflecting film BFIL to be emitted toward the projectionlens 300. Similarly to the incident light of the blue light B on themicro-mirror-type optical modulation device 200B, if the incident angleof the blue image light FB emitted from the micro-mirror-type opticalmodulation device 200B on the side surface 420I is large, the ratio ofthe reflected light can be increased. Furthermore, if the incident angleis increased to a critical angle or larger, the blue image light FB canbe totally reflected.

[0114] On the other hand, of the light entered the blue light-reflectingfilm BFIL, the red light R and the green light G are transmitted by theblue light-reflecting film BFIL to enter the second prism 430. The redlight R and the green light G entered the second prism 430 enter the redlight-reflecting film RFIL. Of the light entered the redlight-reflecting film RFIL, the red light R is reflected by the redlight-reflecting film RFIL, and enters the blue light-reflecting filmBFIL again. The red light R entered again the blue light-reflecting filmBFIL is usually transmitted by the blue light-reflecting film BFIL,however, if the incident angle thereof increases, the light to bereflected is increased, and is totally reflected when the incident anglebecomes a critical angle or larger. The side surfaces 420R and 430I ofthe first and second prisms 420 and 430 on which the bluelight-reflecting film BFIL is formed are set so that the red light Rentered again the blue light-reflecting film BFIL is reflected.Therefore, the red light R entered again the blue light-reflecting filmBFIL is reflected by the blue light-reflecting film BFIL to enter themicro-mirror-type optical modulation device 200R for the red light R.

[0115] The micro-mirror-type optical modulation device 200R forms andemits red image light FR from the entered red light R. The red imagelight FR emitted from the micro-mirror-type optical modulation device200R enters the blue light-reflecting film BFIL so as to be reflected bythe blue light-reflecting film BFIL. The red image light FR reflected bythe blue light-reflecting film BFIL is further reflected by the redlight-reflecting film RFIL to enter the first prism 420, and is emittedtoward the projection lens 300 together with the blue image light FB.

[0116] On the other hand, of the light entered the red light-reflectingfilm RFIL, the green light G is transmitted by the red light-reflectingfilm RFIL to enter the third prism 440. The green light G entered thethird prism 440 passes through the third prism 440 to enter themicro-mirror-type optical modulation device 200G for the green light Gfrom the side surface 440O. The micro-mirror-type optical modulationdevice 200G forms and emits green image light FG from the entered greenlight G. The green image light FG emitted from the micro-mirror-typeoptical modulation device 200G passes through the second prism 430 toenter the first prism 420, and is emitted toward the projection lens 300together with the red image light FR and the blue image light FB.

[0117] By the foregoing description, the red image light FR, the greenimage light FG, and the blue image light FB representing the color imageare emitted from the color light separating-synthesizing prism 400toward the projection lens 300. This allows the color image to beprojected by the projection lens 300.

[0118] Incidentally, the light is allowed to enter the micro-mirror-typeoptical modulation devices 200R, 200G, and 200B at a predeterminedangle, respectively, as described with reference to FIGS. 8(A) and 8(B).

[0119] Since the projector 4000 of the fifth embodiment can alsodecrease ineffective light in the illumination light illuminating thelight application surfaces 202 of the micro-mirror-type opticalmodulation devices 200R, 200G, and 200B, the illumination efficiency ofthe illumination light emitted from the illuminating optical system 100Ccan be increased. In addition, similarly to the first embodiment, theilluminating optical system 100C includes an integrator optical systemcomposed of the first lens array 150, the second lens array 160, and thesuperimposing lens 170. Therefore, since the light application surfaces202 of the micro-mirror-type optical modulation devices 200R, 200G, and200B are uniformly illuminated by the illuminating optical system 100C,an image having uniform brightness can be displayed. In addition, thelength of the optical path of the illuminating optical system can beshortened as compared to that of the conventional illuminating opticalsystem. This can achieve a reduction in size of the projector ascompared to the conventional projector.

[0120] In addition, the projector 4000 of the fifth embodiment displaysa color image by synthesizing the image light emitted from themicro-mirror-type optical modulation devices 200R, 200G, and 200Bcorresponding to the light of three colors, respectively, so that theprojector 4000 can display a color image producing little flickering andhaving high-precision, as compared to the projectors of the first tofourth embodiments.

[0121] Although the example of the color light separating-synthesizingprism 400 of this embodiment formed by the three prisms 420, 430, and440 is shown, it is not limited thereto. For example, the color lightseparating-synthesizing prism may be formed by four prisms. That is, thecolor light separating-synthesizing prism may be a prism as long as itseparates light from the illuminating optical system into a plurality ofcolor light to allow each of the separated color light to enter thecorresponding plurality of micro-mirror-type optical modulation devicesat a predetermined angle, and synthesizes and emits image light of aplurality of colors emitted from the plurality of micro-mirror-typeoptical modulation devices.

[0122] In addition, as the illuminating optical system of thisembodiment, the illuminating optical system 100B of the fourthembodiment in which the color wheel 130 is omitted may be used.

[0123] The present invention is not limited to the above-describedembodiments and modes for carrying out the invention, and can be carriedout in various forms without departing from the sprit and scope of theinvention.

[0124] For example, the DMD used as the micro-mirror-type opticalmodulation device 200 in the above embodiments has been described in acase where it has a restriction such that the optical path of theillumination light IR projected onto the x-y plane parallel to the lightapplication surface 202 is set to face in the direction diagonally tothe lower right of about 45 degrees relative to the x-axis (horizontalaxis h), and that the incident angle of the illumination light IR on thelight application surface 202 is about 20 degrees in a plane includingthe optical path of the illumination light IR and perpendicular to thelight application surface 202. However, the DMD is not limited thereto.For example, the DMD may have a restriction such that the optical pathof the illumination light IR is set to face in the direction having aninclination larger than or smaller than diagonally to the lower right ofabout 45 degrees relative to the x-axis. In addition, the DMD may have arestriction such that the incident angle of the illumination light IR onthe light application surface is smaller or larger than about 20 degreesin a plane including the optical path of the illumination light IR andperpendicular to the light application surface. In this case, theilluminating optical system may include an optical element such that anoutline shape of an emitting surface is a quadrilateral having first andsecond diagonal lines of different lengths (in the above embodiments,the first lens array 150 or a light-transmitting rod 180), and when theillumination light emitted from the optical element obliquely enters thelight application surface at a predetermined angle, the quadrilateralmay be set so that the ratio of two diagonal lines of a quadrilateralillumination region to which the illumination light is applied comescloser to 1 than the ratio of the lengths of the first and seconddiagonal lines.

[0125] In addition, although the example of the projector using themicro-mirror-type optical modulation device has been described in theabove embodiments, the present invention is not limited thereto, and canbe applied to a projector using various types of optical modulationdevices for controlling the direction of emission of the illuminationlight applied to each of pixels according to image information tothereby emit image light representing an image.

What is claimed is:
 1. A projector that projects and displays an image,comprising: an illuminating optical system that emits illuminationlight; an optical modulation device that modulates the illuminationlight emitted from the illuminating optical system; and a projectionoptical system that projects light emitted from the optical modulationdevice, the optical modulation device being an emitting directioncontrol-type optical modulation device that controls a direction ofemission of illumination light applied to a light application surface ofthe optical modulation device according to a given image signal tomodulate the illumination light, thereby emitting image lightrepresenting an image, and the illuminating optical system comprising: alight source; a first condenser lens and a second condenser lens; and afirst lens array having a plurality of first small lenses for dividinglight emitted from the source into a plurality of partial light beamfluxes; and a second lens array having a plurality of second smalllenses corresponding to the plurality of first small lenses.
 2. Theprojector according to claim 1, at least one of the plurality of firstsmall lenses of the first lens array being a decentering lens.
 3. Theprojector according to claim 1, at least one of the plurality of secondsmall lenses of the second lens array being a decentering lens.
 4. Theprojector according to claim 2, at least one of the plurality of secondsmall lenses of the second lens array being a decentering lens.
 5. Theprojector according to claim 1, the illumination optical systemincluding a color wheel having a plurality of color filters rotatablyformed thereon, and the first condenser lens, the color wheel and thesecond condenser lens, respectively arranged between the light sourceand the first lens array.
 6. The projector according to claim 2, theillumination optical system including a color wheel having a pluralityof color filters rotatably formed thereon, and the first condenser lens,the color wheel and the second condenser lens, respectively arrangedbetween the light source and the first lens array.
 7. The projectoraccording to claim 3, the illumination optical system including a colorwheel having a plurality of color filters rotatably formed thereon, andthe first condenser lens, the color wheel and the second condenser lens,respectively arranged between the light source and the first lens array.8. The projector according to claim 1, the illumination optical systemincluding a color wheel having a plurality of color filters rotatablyformed thereon, and the first condenser lens, the color wheel and thesecond condenser lens, respectively arranged between the second lensarray and the optical modulation device.
 9. The projector according toclaim 2, the illumination optical system including a color wheel havinga plurality of color filters rotatably formed thereon, and the firstcondenser lens, the color wheel and the second condenser lens,respectively arranged between the second lens array and the opticalmodulation device.
 10. The projector according to claim 3, theillumination optical system including a color wheel having a pluralityof color filters rotatably formed thereon, and the first condenser lens,the color wheel and the second condenser lens, respectively between thesecond lens array and the optical modulation device.